Andreas - I've recently explored this for a board I designed. IDT's
copnference paper CP-23 is a good tutorial tah's actually easy to
understand. You can get it from theri web site www.idt.com. Another good
publication is IPC'c IPC-2141 which has the formulas for characteristic
impedance of various PWB configurations. It also has much practical info
such as the variation in dieletric constant of PWB materials as actuall
measured over large production samples. Incidentaly the board can out great
although I had to use .004 inch traces to get my approx 62 ohm impedance.

Ray Klein  [log in to unmask]


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